The development of SiC-coated microelectrodes for neural stimulation and recording is proposed. The microelectrodes will employ thin-films of amorphous silicon carbide (a-SiC) as dielectric insulation on iridium shafts. The a-SiC will allow fabrication of stiff, small diameter electrodes that penetrate pia mater without buckling. The electrodes will minimize adverse tissue response from insertion trauma and allow more precise and deeper electrode implantation. Improved chronic biocompatibility and electrochemical stability relative to polymer-insulated electrodes are also expected. The Phase II objective is to demonstrate biocompatibility and functional stability of a-SiC coated microelectrodes and to establish the structural and barrier properties of the a-SiC insulation. Chronic functional studies will be conducted in the cat cortex, spinal cord and cochlear nucleus using stimulus thresholds and unitary action potentials as functional measures. A detailed histopathological evaluation of pulsed and passive electrode sites will be conducted. The mechanical and electrical properties of the electrodes, e.g. buckling strength, insertion force, leakage currents, and electrochemical stability of electrode sites, will be deterrnined by in vitro and in vivo testing. Similar measurements with polymer-insulated electrodes will be used for comparison with a-SiC coated electrodes. Development of electrode designs and manufacturing methods that emphasize spinal cord applications will be undertaken. PROPOSED COMMERCIAL APPLICATION: The intended commercial application is motor and sensory neural prostheses. This will include microelectrodes for intracortical prostheses for vision, hearing and sensation; spinal cord and sacral root prostheses for electromicturition, and peripheral nerve prostheses for motor and sensation. The patient population includes the spinal cord injured, amputees, and those with sensory neural deficits.